1. Field of the Invention
This invention relates generally to air pressure level indicators for tires and the like, and more particularly to such an indicator capable of distinguishing between adequate, marginal and underinflated conditions in a tire.
2. Description of Related Art
The following art defines the present state of this field:
Lindsay, U.S. Pat. No. 3,969,936 describes an inflation valve gauge including a tubular stem having an inner end connected to a pressurized chamber such as formed by a tire, and an outer end provided with an inflation valve; the stem being surrounded by a special, helically wound Bourdon type pressure gauge tube, having an axially inner end penetrating a wall of the tubular stem and an outer end having a pointer overlying an axially directed scale plate; the gauge tube being surrounded by a sleeve which supports the scale plate and is joined to the stem axially inward from the gauge tube; the convolutions of the gauge tube being disposed in close proximity, the confronting wall surfaces of the stem and sleeve being in close proximity to the convolutions of the gauge tube to restrain the gauge tube against extreme mechanical forces tending to damage the gauge tube.
Heyns, U.S. Pat. No. 5,535,623 describes a tire pressure indicator which has a screw-threaded socket for long term but removable association with a tire valve. The body of the indicator houses a movable operator member; actuator member; and resilient member located between the operator member and actuator member. The arrangement is such that the actuator member is held in a "rest" position by the resilient means which is compressed when the actuator member is moved to a "test" position. The degree of compression and resilience of the resilient means are arranged such that the air release pin of the tire valve is depressed only in the event of air pressure in the tire being inadequate to counter the force exerted thereon through the resilient means. The sound of the air escaping in the "test" position is indicative of a low tire pressure.
Mottram, U.S. Pat. No. 3,906,988 describes a combined valve and wheel rim gauge for indicating visually whether the air pressure within the tire is adequate for safe operation. The device includes a flexible diaphragm which controls the movement of an indicating sleeve under varying conditions of internal air pressure to provide a continuous reading of under inflation, proper inflation and over inflation.
Poster, U.S. Pat. No. 1,807,752 describes an automobile tire pressure gauge or indicator, comprising a casing closed at its outer end and having sight openings intermediate its ends. The gauge has a base portion connected to the inner end of the casing. The base portion has an inwardly extending threaded part adapted to detachably engage with a valve stem. The base portion has an opening therethrough registering with the valve stem and having a bar adapted to engage the pin of the valve for maintaining the same open when the base portion is in position. A transparent cylinder mounted in the casing and having an opening through its inner end receives air from the base potion. A piston slidably mounted in the transparent cylinder which has surface portions of different colors is adapted to register past the sight openings during the movement of the piston, and a spring carried in the outer end of the cylinder for engaging against the outer end of the piston urges the latter inwardly against the air pressure.
Stuart, U.S. Pat. No. 1,594,386 describes a removable locked indicating valve stem comprises in combination an expandable air chamber in direct connection with the air in a pneumatic tire and in part a section of valve stem with metallic walls and in part a section of valve stem lined with a flexible rubber member actuated by a pressure spring opposed to the compressed air, an indicating member on the chamber's movable end and actuated by the spring indicating the variance of air pressure in the air chamber, a base member connected in juxtaposition with the pneumatic tire, a shut-off check valve in the base member, a removable tubular member threadably secured to said base member, and enlarged flange on the removable tubular member at its connecting end adapted to prevent it passing through the valve stem hole in the metal rim of the tire wheel from the tire side, and indicating scale on said tubular member in juxtaposition with said indicating member and adapted for indicating the pounds pressure, a sliding tubular member loosely mounted within the outer part of the removable tubular member and adapted to be forced across the opening in the metal walled part of the air chamber by the pressure of air from the supply tube so as to conduct the supply of air to the inlet connecting with the pneumatic tire.
Sweetland, U.S. Pat. No. 1,539,030 describes a pressure indicating device comprising a casing, a sleeve movable within said casing and provided with graduations, a tube having means embedded therein for preventing lateral while permitting longitudinal extension of the tube, and a coiled spring located in the annular space between the sleeve and the tube and arranged to resist the longitudinal extension of the latter.
Gilbough, U.S. Pat. No. 1,309,517 describes in combination with a vehicle wheel and an inflatable tire thereon, a movable pressure operated registering means in operative connection with the tire, and an arm connected to the wheel rim to be moved by movement of said means to project beyond the wheel and strike a stationary part of the vehicle when the tire is not properly inflated.
Harrison et al., U.S. Pat. No. 1,214,714 describes a tire pressure gauge, comprising the combination with the rim of a wheel and the inner tube of a tire, of a bushing tube secured to the rim and passing through the aperture in the same, a tire valve member endwise movable in the bushing tube, means for clamping the inner end of the member to the inner tube, the tire valve member adapted to be pressed outwardly by the inflation of the inner tube, resilient means opposing the outward movement and a tire inflating valve within the tire valve member, the tire valve member having a passage through the same controlled by the tire inflating valve whereby the inner tube of the tire may be inflated through the tire valve member.
Bromberg, U.S. Pat. No. 1,176,338 describes combined tire valve and pressure gauge, the combination of a base piece, an intermediate piece mounted therein provided with a valve seat at its lower end and a central hole longitudinally therethrough serving as an air conductor and with a chamber disposed in one side thereof with a port, the port and central hole terminating in the valve seat, and air valve covering the lower end of the central hole and the port in the valve seat, a plunger reciprocally mounted in the chamber, yielding means engaging with the plunger and means for indicating the pressure on the plunger in connection with the plunger.
Bromberg, U.S. Pat. No. 1,156,268 describes the combination of a tire valve stem, a cylindrical piece secured thereon provided with a curved valve seat with ports leading directly therefrom to the inner surface of said cylindrical piece, a valve mounted in the curved seat, and air conducting tube secured in the cylindrical piece, a valve stem mounted in the tube extending through the outer surface of the cylindrical piece, means for holding the valve seated, a plunger reciprocally mounted in the cylindrical piece, a pressure indicating means in connection therewith and spring for regulating the movement of said plunger.
Hathaway, U.S. Pat. No. 1,1079,704 describes a tire valve barrel having eccentric and parallel air and gage tube bores, the lower end of the latter bore having a primary and an eccentric secondary counter-bore and the upper end of the latter bore terminating short of the tip of the barrel, a mercury tube fitting in the bore and having its outer end closed and seated against the upper end of the bore, the lower end of the tube being open and entering the primary counter-bore, a packing ring in the counter-bore around the end of the tube, a diaphragm having its edges thickened and seated against the shoulder formed by the secondary counter-bore so as to space the diaphragm from the shoulder, and a binding ring screw-threaded into the secondary counter-bore and bearing against the thickened edge of the diaphragm to retain the diaphragm in position, a portion of the valve being cut away to expose the tube and bearing graduations.
The prior art teaches various tire pressure level indicators. However, the prior art does not teach that such a device may be used to show adequate, marginal and underinflated conditions in a tire. The present invention fulfills these needs and provides further related advantages as described in the following summary.